Observation on water body

[Luminance]

 

Took this photo for my assignment and the clear distinct "separation" shown in the midground got me thinking. What causes this to happen? The region of water in the background appears to be "lighter in colour" and smoother as opposed to the region of water in the foreground.

Please kindly comment.

 

Regards.

[CaptainPanic]

Wind.

 

Different parts of a lake can have different winds (because of different trees/buildings on the shore, or just normal turbulence in the air). And different wind means different waves, which in turn give different reflection, which means you observe it as a different color.

 

It can be a small difference in wind speed and/or wind direction, and still be visible on the water.

Edited June 14, 2011 by CaptainPanic

[swansont]

Where was the sun when you took the picture? One candidate is specular reflection, which is brighter because the source is brighter (and will be more strongly polarized than diffuse light, which is why you often use a polarizing filter for outside shots). I think the water looks smoother simply because it's overexposed.

[Luminance]

Hi CaptainPanic! Great to see you again!

 

 

Didn't thought of the wind factor. Thanks for the enlightenment! =)

 

 

EDIT: @Swansont: I can't remember but it was in the noon. On overexposure, I highly doubt so. I remember seeing this sight elsewhere during my journey. And not excluding this of course.

Edited June 14, 2011 by Luminance

[J.C.MacSwell]

In the background where there is more breeze the boundary layer of air is turbulent enough to break the surface tension on the water to some degree.

 

In the foreground the boundary layer is laminar.

[Luminance]

Hi J.C.MacSwell

 

 

Thank you for your reply.

 

 

 

 

If I were to use this photograph to relate a science concept, would water surface tension and laminar flow or specular/diffusion reflecton of light be a more suitable candidate?

 

[J.C.MacSwell]

Hi J.C.MacSwell

 

 

Thank you for your reply.

 

 

 

 

If I were to use this photograph to relate a science concept, would water surface tension and laminar flow or specular/diffusion reflecton of light be a more suitable candidate?

 

Hi Luminance. Welcome to the Forum. I guess it would depend on your interests as both are involved in the photo. For physics, while interested in both, I'm more knowledgeable about boundary layers and in this case "reading the water". to determine and attempt to predict wind patterns.

 

The wind speed in the photo is in the range of 3-5 knots in the background and likely 1-3 in the foreground. There is a wind shear between the two where the background air rises up and over the air in the foreground. The "windline" is probably moving at under 0.5 knots and may in fact be fairly fixed.

 

I would have a very high confidence level for these conditions to state all that even based on one photo. In other conditions it can be much more difficult and less certain.

 

What I find pretty interesting is that even in hurricane force conditions you can see related effects. You can read the effect on the water when a gust of upper airflow breaks the surface tension on the water, and fans out pushing against the "relatively" slower surface air that had established a more laminar boundary layer, even at those greater windspeeds and larger wave conditions.

[Luminance]

Hi J.C.MacSwell

 

Thank you for the further elaboration.

 

My understanding of your explanation is that in the background, the boundary layer of air, which moves at 3 to 5 knots, is turbulent enough to break the surface tension on the water to a certain degree, such that it appears "lighter and smoother", while in the foreground, where the wind speed is 1 to 3 knots, the boundary layer of water is laminar as the water surface tension remains intact due to weaker wind energy. The difference in wind speeds between the two regions creates a wind shear where the air in the background rises up and over the air in the foreground. Additionally, similar effects can be noted in hurricane force conditions, where they can be read when a gust of upper airflow breaks the water surface tension and fans out pushing against the "relatively"(reason for quotation marks?) slower surface air that had established a more laminar boundary layer, even at those greater wind speeds and larger wave conditions.

Is my understanding right?

 

Also, does boundary layer refer to the surface of the water or basically the layer of air above the surface of the water? Or perhaps both, depending on specification?

Edited June 16, 2011 by Luminance

[J.C.MacSwell]

Hi J.C.MacSwell

 

Thank you for the further elaboration.

 

My understanding of your explanation is that in the background, the boundary layer of air, which moves at 3 to 5 knots, is turbulent enough to break the surface tension on the water to a certain degree, such that it appears "lighter and smoother", while in the foreground, where the wind speed is 1 to 3 knots, the boundary layer of water is laminar as the water surface tension remains intact due to weaker wind energy. The difference in wind speeds between the two regions creates a wind shear where the air in the background rises up and over the air in the foreground. Additionally, similar effects can be noted in hurricane force conditions, where they can be read when a gust of upper airflow breaks the water surface tension and fans out pushing against the "relatively"(reason for quotation marks?) slower surface air that had established a more laminar boundary layer, even at those greater wind speeds and larger wave conditions.

Is my understanding right?

 

Also, does boundary layer refer to the surface of the water or basically the layer of air above the surface of the water? Or perhaps both, depending on specification?

 

That's pretty much right although the background is not actually smoother.

 

I was referring to the air for the boundary layers, though of course the water surface and just below is as well.

[Luminance]

That's pretty much right although the background is not actually smoother.

 

I was referring to the air for the boundary layers, though of course the water surface and just below is as well.

 

Alright thank you lots! Yeap I understand the background water isn't actually smoother, thus the term "appears" is applied. =)